Progress Thread Time For A Revival Of My '91 Gt

So, I did some things, and some not so good things this week. I started with redoing the valve lash, and I did it to the 1/2 turn after zero lash. That wasnt that bad, it sounded a little better but still backfiring/popping. While noisily running valvetrain was going on, I checked the vacuum. I was perfect as I've read it to be. 18" Hg and steady as a rock. Minus the valve train noise, it sounded alright. So I went and redid the valve lash again and made sure to go to torque, 18 ftlbs seems to be the consensus on here, and it was within 1 turn from zero lash. Perfect, fire it up and it still pops. I decide to quadruple check the spark plug wires since I just did them to make sure they were all snug, well it turns out number two wasnt snug, so I try to push it on further and it wont seem to get to that last spot, where is sort of snaps into place. So I swap it with number 1, which is about the same length. and now that one is loose. I take one of the old wires and put it on number one, NO MORE backfiring. Wtf, the brand new wire is no good? Oh well, I think I will return these cheap ones and get what I had before, Ford Racing. Granted when I took it for a drive it started backfiring again under load, but no idle popping. I think the old ford wire is just worn. I realyl hope that is it. I will check the codes again this weekend, as the popping under load hit the CEL on again. Good night mustangs.

This weekend I only had a sparce amount of time to tinker and I was able to remedy the lean condition. I checked all the wiring and noticed the ground wire for the O2 sensors was not grounded anywhere so I undid one of the upper intake bolts and bolted that down. After a drive similar to one where the CEL came on, no lights. I will still need to check the codes but it already felt better. I took a video of the sound(s) it is making now. Less backfiring through the intake, except under load. But the one that I hear now concerns me more than that. Any input on what that is or it's cause? I honestly am not sure what it is that is making that noise. Unless its backfiring through the exhaust now. Thanks in advance.

View: https://m.youtube.com/watch?v=iutDAUJ5sUA

Anyone have a thought as to what the deep burbling sound is in the video? I am trying to resolve this issue before I get the new wires tomorrow. While I hope they do the trick, I am not optimistic and want to try and discover the issue in this downtime. Thanks.

I am in the middle of checking the valve lash one more time, I am still somewhat umcomfortable about it. And I pull off the driverside valve cover and number 6 exhaust valve is loose as a goose. I pulled the rockers off to make sure it didn't get ripped out or something and the top of the valve looks a little worn. See below, I don't like it but I don't think it affected the plane of the surface. Thoughts?

The one of the right, it's obvious but I had to point it out. Ha.

So after tightening that rocker down and hooking everything back up, fired right up with no backfiring. However there is backfiring in the exhaust but only on the road under load. That's right direction at least but I think it is misfiring. I'll check firing order once more, but it feels like it isn't missing every time.. just some of the time. Time to check the plugs, I think. Either way it feels good to go for a cruise, the weather is beautiful out today.

Well things are looking up. I checked the plugs, starting with the cylinder that had a motionless exhaust rocker for a short time there They were all in great shape still since I put new ones in since the rebuild, however #6 was fouled beyond belief. So I cleaned it up, threaded it back in and took it for another spin. It ran great. With the only exception being there is a vibration in the steering wheel from ~1500-2500 RPM. I did my homework at the majority of folks stated the Harmonic balancer would be the likely culprit. I took a high fps video of it because it didnt look out of balance to the eye. Well there is definitely some play in the longitudinal direction. If I can get the video to upload I'll post it up for review. Either way its great to have it back running well and drivable at least. Time to make it smooth and pretty.

I was able to get the video of the harmonic balancer uploaded and here is what it looks like. I think it is a little wobbly but I can't tell if its the balancer or something else causing it.

Edit: Link pasted wrong the first time. I can't seem to get the link for the non-mobile version... I'll fix that later...
Edit Edit: Link fixed for non-mobile address.

View: http://youtu.be/96IicQmBctg

A5literMan said:

Did you verify the actual timing? Curious to see if the hub spun on the balancer and throwing your timing off. I don't like that wobble.

Click to expand...

I have not and I am not sure how to visually verify beyond the balancer markings. I would guess just get cylinder 1 to TDC, then check the rotor position relative to the plug? I can do that easy enough.

A5literMan said:

Have you noticed any oil pressure changes or noise from motor? Other than the top end? Makes me think you have a bad balancer or loose pulley. Worse case scenario is there is something wrong internally(thrust bearing,cracked block,crank issue,etc)

Click to expand...

Oil pressure has been steady and noise wise it sounds healthy. If it's something internal I would be shocked since it was just rebuilt, but I suppose crazier things have happened. I'm crossing my fingers it isn't that.

A5literMan said:

Yes check if the tdc markings line up first. Well actually second lol. Run the codes and rule out any wiring/computer/sensor issues. Then verify timing.

Did you reuse the stock balancer? The two piece design tends to have an issue with separation over time. Couple of members on here have run into that issue and caused some tail chasing/head scratching.

Click to expand...

Code check last week after I fixed the backfiring didn't show anything major. Only smog pump related codes popped up, which the system has been removed a long time ago. As for the balancer, it's original but I can pick a new one up easily enough.

A5literMan said:

Also an improperly installed bearing can cause excessive end play of the crankshaft(crank will walk back and forth) which will lead to failure. When the motor was rebuilt was the block sonic checked for cracks?

Click to expand...

I'll have to ask the shop about that, I know it was cleaned and magnifluxed and they told me it checked out. Is there an easy way to tell if there's play? I was trying to push and pull on the balancer last night to see if I could get it to wobble or move manually with no luck.

I picked up a new advance auto store brand balancer to test out.The video of that one is below, it is still a little wobbly which makes me think there might not have been an issue with the other one, or it was just not 100% of the problem. A quick ride down the road and the vibration is still there and roughly at the same caliber. I double checked the timing with the new balancer and it is right around 12* as I had with the other one. I will still check it mechanically tonight or tomorrow. Codes were cleared and I didn't get anything unexpected.
As for what components are in the car;
Original cam
Original distributor
Original coil
Stock injectors
MAF: 70 mm C&L housing with stock meter. I cleaned it a couple weeks ago
TB: BBK 65mm
Walbro 190lbhr fuel pump. (Installed last year, week or two before the engine seized)
- FPR & fuel filter replaced as well
- Fuel pressure gauge is at ~40 psi as it should be.
Brand new plugs, wires, cap, rotor within the month.

Valve train was confirmed correct a couple weeks ago. I had an intake backfire caused by a backed out rocker bolt(must have missed torquing it down during assembly, somehow DERP) The fact that I am typing this all out and that leaves little options makes my gut wrench. If the shop messed up the build or the poor running (backfiring) **** something up I will be at a loss. Let's hope it doesn't come to that.

Edit: Slow motion video instead of full speed.

View: https://youtu.be/UUDHjGBwY7s

The latest update is July has been a very busy month and I was unable to get much time into the car. I did a couple things however and they didn't seem to help too much. I replaced the transmission mount as the other was starting to crack pretty badly. When I went to replace it I found the nuts on it to be hand tight. I am certain I tightened them down with a ratchet so my best guess is the vibration is bad enough to rattle them loose even still. The bolts that held it to the transmission however were still torqued aplenty.

I also replaced the speedometer cable that I managed to melt after getting the engine fired up, back in May. I had run it poorly and it was sitting on the mid-pipe on it's way over to the speed sensor for just a little too long. I plan to spend some more time on this hopefully this weekend. I am also going to call the engine shop that rebuilt it and pick their brains as I am running out of ideas that aren't internal related.

Alright then. So this is difficult to admit, but it would seem that there was never a pilot bearing installed in this crankshaft. I only decided to check because my cousin mentioned it after telling him of my symptoms. I checked some of those old pictures from right after receiving the rebuilt engine from the engine shop. There was one showing there wasn't a bearing installed then and I knew I hadn't installed one myself. I fell victim to the machine shop stating I have everything I need in the boxes they gave me, derp, user error. Hopefully I didn't ruin anything but I definitely have a strong feeling that would cause a vibration. Hopefully THE vibration.

This week I bought a replacement pilot bearing and pulled the car apart once more, once more can't hurt, right? I installed the bearing, put nearly everything back together and now I am sore as hell. The only thing left to do is get the damn transmission all the way in. I could not for the life of me get it to align perfectly, it is only half an inch from fully engaged. I used the alignment tool and I'm sure the splines are engaged just not the bearing with the end of the input shaft. I'll get to finishing it later this week.

Picture tax:


Input shaft play for reference. I don't know if that is too much or how to go about remedying it if it is too much. Just figured I would post this for now.
View: https://youtu.be/2SQE2GVpDYI

Wow, it has been nearly a year since my last posting already? How time flies. The good news is the car has been running amazingly since I finally discovered my misfiring issue last November. It was due to a bad injector. I checked the resistances one night and all were looking good until I hit number eight, it was WAYY out, so likely wide open since the plug was always wet when I was checking. So, I ordered a new set of 19 lb/hr rated injectors and the thing fired up perfectly. No more misfiring, no more rockiness, just smooth revs. It also felt like the power was back to where I was expecting it should be.

In the garage near the DD, '16 ST2. Very comfy but still has some get-up.


Fast forward to the spring where I actually started driving and breaking the engine in. While doing some touching up cosmetically and interior wise. Slow and steady finishes the race, right? Touched up the bumper and side mouldings as the paint was all but gone. I did it just with a rattle can until I get the rest of the body where I want it for a complete paint job. Inspection, no problem. I have about 1200 miles into the rebuild so far and surprisingly have been getting some pretty good mpgs out of it. When I just drive it just to/from work I am nearing 25, mostly highway. That is way better than I used to get.

During a nice cruise around the lake.


I've only had a couple hiccups so far this year. One being my throttle cable somehow popped out of the pedal lever after letting off the pedal one afternoon. The plastic clip didn't look damaged and the pedal looked fine so I popped it back in and we'll see if it stays. Then there wad this morning, the darnedest thing happened that I would never have in a million years guessed could happen. See if you can guess it before I give it away.

The only thing that gave away anything was going on was I heard a slight belt squeal drum up while on the highway. Attentive but not worried, I figured my newly replaced accessory belt was just being noisy for some reason. It stopped after 10-15 seconds. Less than a minute later my battery light lit up and I noticed the volt meter was lower than usual, around 9-10V instead of the 13+ it usually is. **, I am in the middle of a highway where there aren't any good places to pull over, or off. So I keep my eyes on the gauges and limp my way to my job's secondary office which is 5-10 minutes away, instead of 10-15 minutes away to my main office, all while keeping and eye and ear open for anything. As soon as I pulled off the highway I noticed the power steering was out, OKAY the belt probably snapped, oh well. Then the temperature starts to rise steadily, YEA belt is definitely dead. Luckily it was only a mile off the highway and I made it without the temp hitting much more than 1 tick above center. So I open the hood to all it's glory and BAM, there's my alternator trying to jump it's way out the bottom of my engine bay. Hanging there by the tension of the belt wrapped around the tensioner and other accessories. Two of the bracket bolts sheared and dropped my alternator. Luckily it didn't find a way down and out of the engine bay for me to run over. My friend and I are guessing the top bolt backed out, maybe I didn't torque it proper(Probably)? Then the bottom two just couldn't handle the bouncy road and sheared off. Thanks for reading! Time to get this home and fixed back up. Maybe some thread locker this time too, as that was just a crazy turn of events. I am lucky there wasn't more damage.